Scientists bring back deadliest virus in history

By Roger Highfield, Science Editor

12:01AM BST 06 Oct 2005

The deadliest virus on record has been resurrected from a strain of influenza that was preserved in the frozen body of a victim of the 1918 pandemic and triggered a row about whether the benefits of its recreation outweigh the risks.

The replica 1918 "Spanish flu" virus revealed today in the journal Science shows how the pandemic was caused by a strain of bird flu against which humans had no immunity. The virus penetrated deep into the lungs and killed 50 million people worldwide.

The effort to resurrect the virus, which has alarmed some security experts, will help scientists anticipate which viruses could become pandemic and develop new vaccines and treatments.

The announcement comes as the World Health Organisation said that it is only a matter of time before the world suffers another pandemic, and also demonstrates that a current bird flu outbreak has some frightening similarities with the 1918 replica.

Although vaccines offer some immunity and the replica influenza A virus can be fought with two classes of available drug, the reconstructed virus is under lock and key in "stringent safety conditions" at the Centres for Disease Control (CDC) in Atlanta.

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The genetic code of the 1918 virus, however, has been released to the public because scientists claim that the beneficial uses of this knowledge outweigh the dangers posed by its misuse.

Dr Terrence Tumpey of the CDC said his team wanted to understand the biological properties that made the 1918 virus so exceptionally deadly. "We wanted to identify the specific genes responsible for its virulence, with the hope of designing antivirals or other interventions that would work against virulent pandemics." Today's New Scientist asks if this "triumph for virology" is worth the risk of triggering a pandemic. Nature quotes experts who criticise the project for showing how to make "the most effective bioweapons agent now known".

The genetic sequence of the virus was recovered in fragments from lung autopsy tissues from an Inuit woman who was buried in the Alaskan permafrost in 1918.

The 1918 replica kills mice and chicken embryos and it grows rapidly in human lung cells. Most flu viruses that infect humans tend not to be deadly in other species and grow significantly slower in human lung cells.

Dr Jeffery Taubenberger, of the Armed Forces Institute of Pathology in Washington, who was also involved in the project, reports in Nature today that the 1918 virus had several mutations that are found in the H5N1 bird flu strain, which is active in the Far East and has killed around 60 people. Dr Taubenberger said this shows that such viruses can cause serious infection without first combining with a flu strain already adapted to humans, as was previously thought.

One gene that is linked with highly virulent strains of flu is the HA gene responsible for the hemagglutinin protein. This protein helps the flu virus attach to cells and multiply. The gene seemed to be responsible for much of the severe lung damage in Spanish flu victims and this insight could be useful for the development of antiviral treatments, Dr Tumpey said.

He added that the antiviral drugs oseltamivir and amantadine have been shown to be effective against viruses carrying certain genes from the Spanish flu virus. Vaccines that contain the Spanish flu HA gene, as well as another gene from this virus, have also been effective in protecting mice.